The present invention relates to a sensing device which utilizes gyroscopic principles to measure Coriolis force created by the conservation of momentum of driven bodies and, more particularly, to a micro-gyroscopic sensor which vibrationally de-couples a driven mass from the sensing device""s sensing structure.
There are several significant defects in the prior art micro-gyroscopic sensors. Typically, these sensors rely on a single mass element for both driving and sensing functions or rely on multiple mass elements which are physically coupled to a sensor. This coupling of the driving and output motion severely limits the sensitivity of the gyroscope. For example, as the drive element is vibrationally driven, a parameter that affects the sensing mechanism is the amount of vibrational energy which crossovers from the driven element to the sensing electrodes. In the presence of a vibrational crossover, the Coriolis force which is small is difficult to detect, thereby limiting the sensitivity of the sensor.
In all prior art designs there is also a lack of ability to correct for vibrational crossover of the system due to manufacturing tolerances. The problem is worsened by the use of a single support element to couple the driven element to the sensing element. Since the single support element""s length varies during manufacturing, its structure will often generate undesirable signals that corrupt the intended signal.
Furthermore, sensors typically utilize support structures having a plurality of support poles. This configuration leads to significant errors caused by temperature changes. These temperature changes cause thermal expansion of the components which require complicated control algorithms to adjust both the drive and sensing structures.
In one embodiment of the invention, an angular velocity sensor is disclosed having a sensing element and a pair of driven mass drive elements. Each of the driven mass drive elements have a support structure which defines at least one vibrational node. The driven mass drive elements are coupled to the sensing element at the node so as to allow the driven mass drive elements to oscillate about an axis to generate Coriolis forces which are measured by the sensing element, without transmitting oscillation energy to the sensing elements.
In another embodiment of the invention, an angular velocity sensor is disclosed having a sensing element and a plurality of drive elements. The drive elements are coupled to the sensing element through a support structure defining a tuning fork. The tuning fork structure defines at least one vibrational node. The sensing element is coupled to the drive element through the vibrational node. The drive element further oscillates about an axis and has an inertial mass configured to generate Coriolis forces which are measured by the sensor.
In another embodiment of the invention, an angular velocity sensor is disclosed having a support frame, a plurality of drive elements and a motion sensor. The drive elements are coupled to the support frame through a support structure defining a double tuning fork. The support structure defines at least one vibrational node, the support structure being coupled to the support frame at the node. The sensing element is coupled to the support frame while the drive elements oscillate about an axis and has an inertial mass configured to generate Coriolis forces.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. It is however an object of the present invention to provide an improved gyroscopic sensor which overcomes the deficiencies of the prior art micro-machined gyroscopic sensors.